Electrical Transformer Or Induction Device



[No Model.)

7 N. TBSLA. ELECTRICAL TRANSFORMER OR INDUCTION DEVICE.

7 No. 433,702. Patented Aug. 5, 1890.

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UNITED STATES NIKOLA TESLA, OF NE\V YORK, N. Y., ASSIGNOR TO PATENTOFFICE.

THE TESLA ELECTRIC COMPANY, OF SAME PLACE.

SPECIFICATION forming part of Letters Patent No. 433,702, dated. August5, 1890.

' Apnlicat ion filed March 26. 1890. Serial No. 345,390. (No model.)

To all whom it may concern;

Be it known that I, NIKOLA TESLA, a subj ect of the Emperor ofAustria-Ilungary, from Smiljan, Lika, border country of Austria-Hungary, residing at New York, in the county and State of New York, haveinvented certain new and useful Improvements in Electrical Transformersorlnduction Devices, of which the following is a specification,reference beinghad to the drawings accompanying and forming a part ofthe same.

This invention is an improvement in electrical transformers orconverters, and has for its main objects the provision of means forsecuring, first, a phase difference between the primary and secondarycurrents adapted to the operation of my alternating-current motors andother like purposes, and, second, a constant current for all loadsimposed upon the secondary.

In transformers as constructed now and heretofore it will be found thatthe electromotive force of the secondary very nearly coincides with thatof the primary, being, however, of opposite sign. At the same time thecurrents, both primary and secondary, lag behind their respectiveelectro-motive forces; but as this lag is practically or nearly the samein the case of each it follows that the maximum and minimum of theprimary and secondary currents will nearly coincide, but differ in signor direction, provided the secondary be not loaded or if it containdevices having the property of self-induction. On the other hand, thelag of the primarybehind the impressed electro-niotive force may bediminished by loading the secondary with a noninductive or deadresistance-such as incandescent lam ps-whereby the time interval betweenthe maximum or the minimum periods of the primary and secondary currentsis increased. This time interval, however, is limited, and the resultsobtained by phase difference in the operation of such devices as myalternating-current motors can only be approximately realized by suchmeans of producing or securing this difference, as above indicated, forit is desirable in such cases that there should exist between theprimary and secondary currents, or those which, however cuits of atransformer into the closest possi- 6o ble relations, as has hithertobeen done, I protect in a measure the secondary from the inductiveaction or effect of the primary bysurrounding either the primary or thesecondary with a comparatively-thin magnetic shield or screen. Underthese conditions or circumstances, as long as the primary current has asmall value, the shield protects the secondary; but as soon as theprimary current has reached a certain strength, which is arbitrarilydeter- 7o mined, th eprotectingmagnetic shield becomes saturated and theinductive action upon the secondary begins. Itresults, therefore, thatthe secondary current begins to flow at a certain fraction of a periodlater than it would without the interposed shield, and since thisretardation may be obtained without necessarily. retarding the primarycurrent also, an additional lag is secured, and the time intervalbetween the maximum or minimum periods of the primary and secondarycurrents is increased. I have further discovered that such a transformermay, by properly proportioning its several elements and determining in amanner well understood the proper relations between the primary andsecondary windings, the thickness of the magnetic shield, and otherconditions, be constructed to yield a constant current at all loads. N oprecise rules can be given for the specific construction and proportionsfor securing the best results, as this is a matter determined byexperiment and calculation in particular cases; but the general plan ofconstruction which I have described will be foundunder all conditions toconduce to the attainment of this result.

In the accompanying drawings I have illus trated the construction aboveset forth.

Figure 1 is a cr0ss-section of a transformer embodying my improvement.Fig. 2 is a simi- I0 To more perfectly 5 5 lar view of a modified formof transformer, showing diagrammatically the manner of using the same.

A A is the main core of the transformer, composed of a ring of softannealed and insulated or oxidized iron Wire. Upon this core is woundthe secondary circuit or. coil B B. This latter is then covered with alayer or layers of annealed and insulated iron wires O O, wound in adirection at right angles to said secondary coil. Over the whole is thenwound the primary coil or wire D D. From the nature of this constructionit will soon be obvious that as long as the shield formed by the wires 0is below magnetic saturation the secondary coil or circuit iseffectually protected or shielded from the inductive influence of theprimary, although I would state that on open circuit it may exhibit someelectro-motive force. Vhen the strength of the primary reaches a certainvalue, the shield O, becoming saturated, ceases to protect the secondaryfrom inductive action, and current is in consequence developed, therein.For similar reasons, when the primary current weakens, the weakening ofthe secondary is retarded to the same or approximately the same extent.

The specific construction of the transformer is largely immaterial. InFig. 2, for example, the core A is built up of thin insulated ironplates or disks. The primary circuit D is wound next thecore A. Overthis is applied the shield O, which in this case is made up of thinstrips or plates of iron properly insulated and surrounding the primary,forming a closed magnetic circuit. The secondary B is wound over theshield O. In Fig. 2, also, E is a source of alternating or rapidlychanging currents. The primary of the transformer is connected with thecircuit of the generator.

.F is a two-circuit alternating-current n10- tor, one of the circuitsbeing connected with the main circuit from the source E, and the otherbeing supplied with currents from the secondary of the transformer.

Having now described my i I claim is 1. In an electrical transformer orinduction device, the combination, with the main magnetic core and theprimary and secondary coils or circuits, of a magnetic shield or screeninterposed between said coils, as herein set forth.

2. In an electrical transformer or inductive device, the combination,with the magnetic core and the primary and secondary coils or circuits,of a magnetic shield or screen surrounding one of said coils only, asset forth.

3. In an electrical transformer or induction device, the combination,with the magnetic core and the primary and secondary coils woundthereon,of a magnetic shield or screen wound on or built up around oneonly of said coils, as described.

4. In an electrical transformer or induction device, the combination,with a main laminated magnetic core and primary and secondary coilsthereon, of a subdivided or laminated magnetic shield or screeninterposed between the coils, as set forth.

5. I11 an electrical transformer, the combination, with a magnetic coreand primary and secondary coils wound thereon, of a magnetic shield orscreen interposed between said coils and surrounding one of them andadapted to be or capable of being magnetically saturated by apredetermined current strength below the maximum in the primary, as setforth.

nvention, what NIKOLA TESLA.

- Witnesses:

RoBT. F. GAYLORD, PARKER W. PAGE.

